Telemetric data transmission system



Oct. 5, 1948. F. s. KINKEAD :1 AL

TELEIETRIC DATA TRANSMISSION SYSTEI 9 Sheets-Sheet 1 Filed Jan. 11, 1944 F. S KIA/READ DECEASED HI 7.4 S, KINKEAD Hi8 ADMIN/5T TR/X E M: SM! TH j 6 1 A T TORNI'Y Oct. 5, 1948. F. s. KINKEAD ETAL TELEMETRIC DATA TRANSMISSION SYSTEI 3 a Nut 4! TORNEY Oct. 5, 1948. F. s. KINKEAD ET AL 2,450,516

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Oct. 5, 1948. F. s. KINKEAD ETAL 2,450,516

TELEMETRIC DATA TRANSMISSION SYSTEM Filed Jan. 11, 1944 9 Sheets-Sheet 4 [NYE N TORS A T TORNE) Oct. 5, 1948. s, KlNKEAD r 2,450,516

TELEMETRIC DATA TRANSMISSION SYSTEM Filed-Jan. 11, 1944 9 Sheets-Sheet 5 POLA RIZLD POLARIZE'D (0NLYJ snow/v) THROUGH 20 CIRCUITS (our .3 snamv) 20 CIRCUITS r. s. KIA/READ nausea mm s. KIN/(40 HIS mum/51mm mvewrons: 5: flggfgf r.J. swam ar in. 3mm

ATTORNEY Oct. 5, 1948. F. s. KINKEAD ET AL TELEMETRIC DATA TRANSMISSION SYSTEM 9 Sheets-Sheet 6 Filed Jan. 11, 1944 KIA/K540 DECEASED S KIN/(E40 HIS ADMIN/S m4 TRl/Y IN VEN TOPS E MELHU/SH W A .PHELFS F.J. SINGER E M. SMITH ATTORNEY Oct. 5, 1948. F. S.,KINKEAD EIAL TELEMETHIC DATA TRANSMISSION SYSTEM DECEASED .S KI HIS MMINISTRAIWIX LHUISH HELPS F J SINW MITH L WA

' AT TORIIEV 9 sh eetbsheet 9 Filed Jan. 11, 1944 Fla /3 FIG/2 TEIITH 0 EGREE COIIE HUNDREDTH DEQREE CODE CIA! NOS CAM NOS m s u u H 4 w. u n H m J, 5 m M Z n n m n E M MMMZZWZ r0 ZZZZZ m n w 0 M E u "I m I'M m. n: YP 5671.901 67180/234 mm" s L: .323 uQvod hi? 3 33%: a w Y2 w--w mm 3 3 3 v73 Cl NN My DEGREE [ONES DEGREE CODE CAM NOS.

NUMIER IN EACH TflANS CHANNEL N05. 20' I0!!! VERN/ER IS ON IERO If S KIN/(E40 DECEASED RITA S. k/NKEAD HIS ADMIN/3TH! TR/X INVENTORS' E.J. SINGEH E. M SMITH Patented Oct. 5, 1948 UNITED STATES PATENT I OFFICE TELEMETRIC DATA TRANSMISSION SYSTEM York Application January 11, 1944, Serial No. 517,824

The invention relates to means for and methods of maintaining a receiving station continuously informed of magnitudes observed or measured at a transmitting station; more specifically it relates to improvements in systems for and methods of transmitting and in expediting the transmission of permutationally coded multifrequency alternatingcurrent electrical impuls s, c s ing to multidigit numbers defining an observation or measurement, from a first station to a second station.

A system arranged for transmitting almost instantaneously permutation code direct current impulses corresponding to a multidigit number from a first station to a second station is disclosed in a patent application by Kinkead et al., Serial No. 464,564 filed November 5, 1942, and which has become Patent No. 2,406,384, Aug. 2'1, 1946. The exemplary system herein disclosed employs permutation codes of alternating currents of different frequencies instead of direct current in transmitting the impulses between stations and includes new transmission and selecting features.

The multidigit number which is defined by the permutation code impulses of alternating current transmitted between stations may correspond to data readings at one of the stations. The multidigit number may also designate called subscribers in a communication switching system. The multidigit number may represent gradations of shade ina picture. In fact, the multidigit number may represent a wide variety of things and conditions dependent upon the system wherein the invention herein ls-applied.

An object of this invention is the improvement of systems for transmitting data such'as data represented by plural digit numbers from a first station to a second station.

Another object of the invention herein is the transmission of permutation codes of alternating current electrical impulses of various frequencies defining multid'igit numbers which may, for instance. represent observed data from a first station to a second station almost instantaneously with the establishment of the data which define the multidigitnumbers.

A feature of the invention herein is the employment of various permutation code combinations of different frequencies of alternating current to define separate portions of the same number, and transmitting the various permutation code combinations of currents of different frequencies simultaneously over a plurality of transmission channels to define an observation or measurement made at an observing station in terms of multi-- 7 claims. (Cl. 177-351) digit numbers to a receiving station as nearly as possible concurrently with the observations.

A further feature of the invention comprises means and methods for generating an alternating current of a single frequency at a receiving station, transmitting said current over a transmission path extending to a second station, converting the current of a single frequency into a current of five difierent frequencies in a harmonic generator located at the second station, selectin various combinations of the frequencies m accordance with separate permutation codes to define separate portions of multidigit numbers corresponding to observations at the second station,

retransmitting alt-emating currents of the various code combinationsof frequencies defining the separate portions of the multidigit numbers simultaneously from the second station back to the receiving station and transmitting the currents of various code combinations of frequencies re-' ceived at the receiving station through selectin devices at the receiving station to control indieating devices corresponding to the multidigit number.

A further feature of the invention'is the dividing of eachof the multidigit numbers representin the data to be transmitted between stations into a plurality of subgroups of digits, the number of digits in each subgroup and the number of subgroups being chosen in such manner as to minimize the number of channels required for the almost instantaneous transmission of alternating current impulses of various frequencies in accordance with a permutation code to identify the multidigit number at the receiving station.

A further feature of this invention is the separation of a multidigit number having fourdigits into three subgroups of digits, the assigning of two separate multielement permutation codes and two separate transmission circuits to three subgroups, the assigning of a separate code combination to each number in each subgroup and the assigning of a number of separate alternating current channels corresponding to the number of elements in each multielement permutation code for each transmission circuit so as to permit the simultaneous transmission of code combinations of different groups of frequencies of alternating current impulses to define separate portions of the multidigit number at the receiving station .at almost the same instant that an observation or measurement is made at the observing station.

Another feature of this invention is an alternating current transmission path comprising five separate channels for five different altemating current; frequencies arranged for the transmission at times of permutation code signal combinations defining single digit numbers while varying the current frequency combinations impressed on only four of the five channels and for the transmission at other times of permutation code signal combinations defining two-digit numbers requiring the varying of the frequency combinations impressed on all five channels.

I Another feature of this invention is the disabling of the apparatus controlled in response to the alternating current signal elements defining the single digit number when alternating current signal elements intended for the control of apparatus responsive to the two-digit number are transmitted and vice versa. These and other features of the invention will become apparent from the following description when read with reference to the associated drawings, in which Figs. 1 to 6, which show the overall circuit, should be arranged as indicated in the blockdiagram per Fig. 7. Figs. 1 and 2, as indicated in Fig. 7, show equipment which is located at the observing or measuring station and Figs. 3 to 6 show the circuit interconnecting the observing or measuring station and the receiving station and the apparatus at the receiving station.

Fig. 1. represents an observing instrument, in this particular embodiment a telescope, mounted on a device for measuring the angle between the line of sight through the telescope and a base line and translating the measurement into multielement permutation code settings of the three groups of cams, shown in the figure, which define the measurement. Each group of cams controls an individual set of electrical contacts which are ing the observing and receivin station, as well as a harmonic generator, band-pass filtering equipment, and amplifying equipment at the observing station;

Fig. 3 shows the line equipment connecting the 'observing station with the receiving station, as well as an oscillator, shown in the center of the figure, for generating a single frequency alternatin current and shows also two amplifiers, one associated with each incoming side circuit, two sets of band-pass filters, two sets of amplifierrectifiers connected individually to the filters and two sets of code receiving relays connected to the rectifiers;

Fig. 4 shows two selecting circuits located at thereceiving station;

Fig. 5 shows a third selecting circuit located at the receiving station;

Fig. 6 shows an indicating circuit located at the receiving station;

Fig. 7 is a diagram showing the manner in which Figs. 1 to 6 should be arranged, each in relation to the other, to form an operative system;

Fig. 8 is a diagram illustrating an embodiment of the invention herein, employed when the invention is used in an-artillery range finding system. In such an arrangement, one set of equipment such as-Fig. 1 and Fig. 2 combined would be required at each of two observing stations and two sets of receiving equipment, such as Figs. 3 to 6 combined, would be located at each receiving station. The position of the target would be fixed by means of a base line of known length interconnectin the two measuring instruments per Fig. 1 and the magnitude of each angle between the base line and the line of sight to the target at a particular instrument. The system will provide an almost instantaneous and continuous record of the position of the target as the position of the target changes;

Figs. 9, 10 and 11 show the cam cuttings of the three sets of cams in Fig. 1; and

Figs. 12, 13 and 14 show the codes set up on each of the three sets of cams in Fig. 1 to define the different portions of the multidigit number.

General description A short general description of the invention will now be given before proceeding with the detailed, description thereof.

The central or receiving station and the measuring or observing station are interconnected by two pairs of conductors, Figs. 2 and 3, which pairs of conductors are also interconnected at each end by balanced transformer coils in a welleknown manner to provide a third circuit known as a phantom 'circuit. An oscillator, shown in the middle of Fig. 3, generating a single frequency current, is connected through an amplifier to tiie phantom circuit at the receiving station. At the observing station the single frequency current is transmitted from the output of the phantom circuit, as shown in Fig. 2, to a harmonic generator which translate alternating current of a single frequency into alternating current of a number of frequencies of which five are employed. All five are employed as elements in one permutation code and four of the five as elements in a second permutation code.

The output of the harmonic generator is impressed on five band-pass filters connected in parallel. The outputs of the band-pass filters are connected by conductors interconnecting Fig. 2 and Fig. 1 to three difierent sets of cam-controlled contacts on the measuring instrument at the observing station. In the particular embodiment of the invention described herein, the measuring instrument is arranged to measure any of the angles in a 360-degree range. The full 360- degree scale is divided into eighteen ZO-degree zones. In operating the system of the invention in actual practice, a well-known counting circuit is employed at the receiving station which counts and indicates at the receiving station the actual 20-degree zone in which an observation or measurement is momentarily being made. The particular 20-degree zone in which a series of measurements are started is disclosed to the attendant at the receiving station by means of some complementary communication facility such as by telephone or telegraph.

A measurement made at the observing station within any 20-degree zone may be expressed by any four-digit number in the range from 00.00 to 19.99. The number is first separated into three parts. A first code is assigned to the digits in the hundredths place. A second code is assigned to the digits in the other three places combined, namely, the tenths place, the units place and the tens place. To define any of the hundredths digits ten code combinations are required. A four-element, two-condition code is assigned for this purpose. This provides a total of 2 or sixteen code combinations-of which ten only are employed. To define the digits for the other three places, a total of thirty code combinations is required. Ten of these are used to define the ten digits in the tenths place and twenty are used to'define the twenty full units numbers in the range from to 19. A five-element, two-condition code providing 2 or thirty-two code combinations is provided for this purpose, of which thirty only are employed.

Two two-wire side circuits of the phantom group are employed in transmitting the signals of the two permutation lcodes. One of the side circuits is used in transmitting the permutation code signals which define the digits in the hundredths of a degree position. The other of the side circuits is used in transmitting the permutation code signals which define the digits in the other three places. The circuit which is used for the code signals defining the hundredths digits consists of four channels, one for each element of the four-element permutation code. The circuit which is used for the other three digits has five channels, one for each element of the fiveelement permutation code.

In this invention, in order to avoid loss of time in defining measurements at the receiving station, all of the digits in the four-digit number in the range from 00.00 to 19.99, 20.00 to 39.99 or 340.00 to 359.99 are defined simultaneously at the receiving station and at almost the same instant that the measurement is made at the observing station. And in order to effect economy in the number of transmission circuits employed, only two two-wire transmission circuits, one having four alternating current channels and the other having five alternating current channels are used. It would appearv that the limit of such a system, unless the transmission of codes defining certain of the digits in different places in .the number were effected on a time discrimination basis at a sacrifice in time, would be the simultaneous definition of a three-digit number in the range from 000 to 319. That is to say, the dour-element channel could. define digits in the right-hand position in the range from 0 to 9 and particular full units digit from 0 to 19 is effected at the receiving station during a portion of the interval while a selection of a tenths zone in the range from 95 hundredths to 04 hundredths, which will be termed the zero tenths position herein, is maintained.

In addition. to the selector for the hundredths digits mentioned above, two separate multisw'itch selectors, one for tenths of a unit and one for full units from 0 to' 19, are employed at the receiving station. Advantage is taken 01' the'fact that the selection to be made by the tenths selector is always the same, viz., the selection for zero the five-element channel could define digits in the two left-hand positions in the number in the range from 0 to 31, if both portions of the number were to be defined simultaneously and at almost the same instant that the observation was made. The manner in which all of the digits in any number from 00.00 to 19.99 are defined at the receiving station simultaneously and at almost the same instant that the measurement is being made at the observing station, while employing onlytwo two-wire circuits, one having four and the other having five alternating current channels involves a novel arrangement of the five channel circuit and a novelarrang'ement of threediflerent selecting circuits at the receiving station.

The four-channel circuit which, as mentioned above, defines the digits in the right-hand or hundredths position, transmits the four alternating current signal elements. of the four-element permutation code simultaneously to a single tour-switch selecting circuit at the receiving station. As the hundredths digits change in accordance with the changing measurements, the four-channel cincuit and the four-switch selector which it controls and to which it is permanently connected are available at all times to transmit code combinations and] make almost instantaneous selections defining the measurement.

' In the case of the five-element channeland the five-element code, as mentioned above, ten of the five-element code combinations define the digits in the tenths nosition and twentv define the tenths, when a full units selection is made. One

of the five-element code combinations is a combination in which no current istransmitted for any of the five-signal elements. bination is assignedv to zero tenths. It is not necessary to actually transmit any current impulses over the five-element circuit in order to effect the selection of the zero tenths. This selection is efiected by the tenths selector in re-- sponse to the transmission of no current impulses over the five-element circuit. During a portion of theinterval, while the measuring instrument is in the zero tenths zone, viz., while it is also in the region of zero hundredths, the full units selector is conditioned through the cooperation of both the hundredths'selector and the tenths selector to receive a code defining the full units. This will involve the transmission of five-element code signals over the five-element circuit to which both the tenths-of-a-degree selector and the full units selector are connected. This tends to affect the zero tenths selection. But while this condition prevails the 'tenths-of-a-unit selector is conditioned by the hundredths-of-aunit selector so that the tenths of a unit selection or zero tenths remains unaflected.

It is thus possible by means of the invention herein to control both the tenths-of-a-degree selector and the full units selector by means of one transmission circuit so that each efiects a selection simultaneously. The zero tenths selection by the tenths selector is maintained while the full units code is being received over the same circuit which serves both.

In the drawings, the output side of each 0! four of the five band-pass filters-connected to the output of the harmonic generator in the middle are impressed on the input side of the tour bandpass filters shown at the left of Fig. 2. They are impressed on the primary of the transformer con nected to the output of the four band-pass filters at. the left of Pic. 2 in mar inal lihrnnoh-i-hn This code com-' secondary of the transformer, and through a line amplifier, on the upper side circuit extending to the receiving station. In the receiving station they are amplified in the top amplifier shown in Fig. 3 and are impressed through the four bandpass filters connected to the output of the amplifier on individual amplifier-rectifiers to operate individual relays connected to the output of the amplifier-rectifier. The four' selecting relays shown in the rightupper portion of Fig. 3 control a selecting circuit shown at the top of Fig. 4, comprising four sets of relay switches. which eifect a selection of a hundredths of a degree indicator in the indicator circuit of Fig. 6.

The cams for the hundredths of a degree codes are arranged so that in turning through one-half of a revolution they establish ten diilferent codes to define ten different hundredths of a degree and in turning through the second half of a revolution they repeat the codes in reverse order to define each of the succeeding ten hundredths of a degree. This may be seen from reference to Fig. 12. Reference to Fig. 12 shows also that a change in not more than one signal element is required in transitions between code combinations. This will result in a minimum of inductive disturbance during transmission of the alternating current combinations in accordance'with the codes and a minimum number of changes in the switching apparatus which is one of the important aspects of the invention herein.

Attention is particularly called to the fact that although the code combinations which define the tenths of a degree digits are five-element code combinations, the particular code combinations which are assigned for the tenths of a degree are combinations in which current is never transmitted for the fifth element so that the fifth channel remains open or non-conducting at all times while defining tenths of a degree digits. This may be seen from reference to Fig. 13. Fig. 13 shows ten code combinations of the five-element code defining tenths of a degree and Fig. 14 shows twenty code combinations of the same code used in defining the full unit degrees from to 19.

The output side of each of four of the five band-pass filters connected to the output of the harmonic generator in the middle of Fig. 2 is connected to a different contact controlled by each of the four tenths of a degree cams secured to the upper horizontal cam shaft in Fig. 1. A different code combination of four of the five frequencies is passed for each of ten difierent cam setting combinations within each full degree zone to define each tenth of a degree. The selected code combination of frequencies is passed by four of the five band-pass filters at the right of Fig. 2 through the transformer connecting the output of the right-hand band-pass filters in parallel, through the line amplifier at the upper right of Fig. 2, through the lower of the two side circuits, to the circuit per Fig. 3 at the receiving station. They are amplified in the bottom amplifier in Fig. 3, selected by four of the five band-pass filters connected in parallel to the bottom amplifier, amplified and rectified in the corresponding amplifier-rectifiers, connected to the output of the band-pass filters and then they operate four of the five relays connected to the rectifiers in various combinations while the fifth remains unchanged in a particular position in accordance with the code. The relays in turn control the lower selecting circuit shown in Fig. 4 which selects the tenth of a degree corresponding to 8 the particular code combination or the circular lamp band indicator per Fig. 6.

The output side of each of the five band-pass filters connected to the output of the harmonic 1 generator inthe middle of Fig. 2 is connected at intervals, when full degree code signal combinations are to be transmitted, by means of a camcontrolled switch at the left in Fig. 1 to a different contact controlled by each of the five full unit degree cams, which are the five cams secured to the vertical cam shaft in Fig. 1. A different code combination of currents of the five frequencies is passed for each of the twenty different combinations of cam settings of the full units cams. Currents of frequencies in accordance with the particular code combinations are transmitted over the same circuit heretofore described, except that conditions on all five channels are varied in defining the full degrees. The five relays at the bottom right of Fig. 3 are operated in accordance with the code. The settings of these relays in turn control the selecting circuit in Fig. 5 to indicate the corresponding full degree position.

The selecting mechanism per Fig. 5 for the full units selection is locked at all times except during a short interval while the measuring instrument is in the region of zero tenths of a degree and zero hundredths of a degree. This-interval is determined by the cooperation of the tenths selector and the hundredths selector.

In the case of the five-element channel, ordinarily the tenths of a degree cam contacts in Fig. 1 are connected to itstransmitting circuit and the full degree contacts are disconnected except for the short interval while full degree code signal combinations are to be transmitted. This is accomplished by means of switch I45 in Fig. 1 which is controlled by cam I25. The zero tenths of a degree zone extends from hundredths to 04 hundredths. As shown in the top line of Fig. 13 no current is transmitted for any element of this code combination. Cam I25 operates switch lever I45 to close contacts I60 to.

168 to connect the five channels to the full degree cams Iii to H5 during a portion of the interval while the tenths of a degree cams are in the zero tenth zone. At all other times the full unit degree cams are disconnected from the channel.

The cooperation of the hundredthsof a degree selecting circuit at the top of Fig. 4 and the tenths of a degree selecting circuit at the bottom of Fig. 4 controls the indicator circuit in Fig. 6 so a to light a particular one of the hundred lamps in the lamp bank 600 to identify the particular hundredth of a degree position corresponding to the line of sight through the telescope. The selecting circuit per Fig. 5 alone selects an indicator to designate the corresponding full degree position.

The mechanism is arranged to provide a proper indication whether the movement of the target and the measuring instrument is such-that the measured angle is increasing or decreasing.

Detailed description Refer now to Figs. 1, 2 and 3. A telescope IIJI is directed at the target. The particular twenty-degree zone within which the line of sight to the target is located is made known to the attendant at the central station by means of a separate telephone or telegraph circuit (not shown). Once the target is sighted. the telescope {0| is continuousl directed at the target by the observer who will turn the Vernier crank I00 to rotate hai't I02 in such manner as to maintain the lin of sight through the telescope on the target. As the vernier crank is turned, the telescope is rotated by means of worm I03 which is rigidly secured to the vernier shaft. Worm I03 engages with a circular rack gear I04 on the outer surface of a disc I05 to the center of which the telescope IN is rigidly secured by means of the U-shaped leveling and clamping device I 08. One complete rotation of the vernier shaft I rotate telescope IOI through one degree through the cooperation of worm gear I03 and rack gear I04, which have a ratio of 360 to i. As telescope IOI is rotated, the radial horizontal arm I01 rigidly secured to disc I is rotated with it. The outer end of radial arm I01 forms .a bearing for the upper end of vertical cam shaft I0 8 the lower end of which is supported and secured in a bearing in the right-hand end of rotatable radial arm I0'IA. The left-hand end of the lower radial arm I0IA is secured in a bearing, not shown, in vertical alignment with the vertical axis of the disc I05 about which radial arm I0'IA rotates as a center. A pinion I09 is secured to shaft I08 in position intermediate the ends of the shaft I08 to engage ring gear IIO which is concentric with disc I05 and rigidly secured to a tripod, not shown, used to support the observing instrument and its associated mechanism.

shown, fixed in a bearing in alignment with the vertical axis of disc I05. Vertical bell crank cam follower shaft I50 is secured in an upper bearing at the right-hand end of rotatable radial arm contacts II8 to I20 are spaced vertically alongplate I54. The right-hand end of each of the bell crank followers is maintained in engagement with its respective cam by a tensioned spring such as I55, the left-hand end of which is secured to the left-hand end of the follower and the righthand end of which is secured to fixed follower shaft I50. Where the periphery of any of cams III to H5 is depressed the corresponding follower is rotated clockwise to disengage from its corresponding contact and the contact is open. When the periphery is raised the corresponding follower is rotated in a counter-clockwise direction to engage the contact and the contact is closed. The entire assembly comprising radial arms I01, I0'IA and I52, vertical shafts I08 and tionship between the units of the revolving assembly. I

As the shaft I08 revolves, pinion I08 engages ring gear I I0. Thus shaft I08 while revolving about hevertical axis of disc I05 and telescope IN as a center, rotates also about its own center. The ratio of the gear IIO to gear I08 is such that shaft I08 rotates about its own axis once while revolving through twenty degrees about the vertical axis of disc I05. The five full degree cams II I to H5 are arranged to control their corresponding contacts through their associated bell crank followers I I IA to II5A in accordance with the permutation code shown in Fig. 14 so as to transmit twenty different combinations of a group of five alternating current frequencies for each rotation of shaft I08 to identify each of the twenty different full degree divisions within each of the eighteen sectors into which the observing circle is assumed to bedivided. Each of cams I II to 5 therefore is divided into twenty equal segments, each arranged to either open or close its respective contact to provide twenty code combinations for each revolution of shaft I08 to define each of the twenty degrees as indicated in Fig. 14.

Mounted on thehorlzontal vernier crank shaft v I02 are five cams I 2| to I25. Shaft I02 and each of cams I2I to I25 rotate once for each onedegree change in position of telescope IOI. Four of these cams, I2I to I24, are used to control the ten different permutation code combinations of settings of their bell crank followers and the contacts controlled by their followers. The fifth cam, cam I25, is used in controlling a switch I45 the function of which is to control the times of transmission of the full degree code combinations. It will be explained below. Cam shaft I is coupled to cam shaft I02 through spur gears I58 and I58 which have a ratio of one to five. Mounted on shaft I40 are the four hundredth of a degree cams I3I to I34 which control their respective contacts Hi to I44 through four bell crank levers. In turning through one-half of a rotation cams I3I to I34 set up ten different code combinations of contacts I to I44 to define each of the ten hundredths of a degree divisions in each tenth of a degree. In turning through the second half of a revolutionthe code combinations are repeated in reverse order. The code is shown in Fig. 12. Reference to this figure shows that there are only ten distinctive codes. These are shown in the top ten horizontal lines of Fig. 12.

The codes are repeated in reverse order. The code shown in the eleventh line from the top is the same as the code in the tenth line from the top. The code shown in the first horizontal line is not repeated until it appears in the twentieth line. Reference to succeeding codes shows that not more than a single element changes condition at any time.

Transmission of hundredths of a degree information The manner in which the hundredths of a degree information is transmitted from the observing station to the central station will first be described.

Key 310, Fig, 3, is closed which establishes a circuit from grounded battery 3' through key 310, over the four conductors 360, 36I, 382 and 383 in parallel, through conductor 252 in Fig. 2 to parallel branches. One branch extends is connected to the mid-point of the secondaries 392 and 393 of transformers 368 and 369 respectively. Conductors 369 to 383 which connect the secondaries of transformers 392 and 393 to the observing station form a phantom group comprising two side circuits: Conductors 369 and 38I form one side circuit. Conductors 362 and 363 form the second side circuit. The first side circuit is terminated in winding 249 of transformer 2|5; the second'side circuit is terminated in winding 259 of transformer 2", The midpoints of coils 249 and 259 are interconnected through coil 25I of transformer H9. The single frequency voltage provided by oscillator 399 is impressed through the secondary of transformer 2 I 9 on the input of harmonic generator 229. Milliammeter 223 in the circuit interconnecting the secondary of transformer 2I9 and the input of harmonic generator 229 provides an indication oi the amount of current flowing in the input circuit of the harmonic generator. In response to the alternating voltage of eighty-five cycles impressed on the input of the harmonic generator 229, alternating voltages of the odd harmonics of eighty-five cycles are impressed on the input of band-pass filters 295 to 299. Band-pass filters 295 to 299 are arranged to pass current of 425, 595, 765, 935 and 1105 cycles or th fifth to thirteenth odd harmonics respectively.

When the cams I3I to I34 raise their respective followers in accordance with the various permutation code combinations, contacts Hi to I44 respectively. are closed. When contact I is closed. a circuit is established which interconnects the output of band-pass filter 299 which passes current of 1105 'cycles through resistance 239, conductor I39, contact I4I, conductor I39, resistance 23I, and filter 29i, which also passes current of 1105 cycles to the primary' winding of transformer 224. When cam I32 raises its follower contact I42 is closed. The output of bandpass filter 298, 935 cycles, is connected through resistance 238. conductor I31, contact I42, eonductor I31 and band-pass filter 292, 935 cycles, to the primary of transformer 224. When cam I33 raises its follower contact I43 is closed. This establishes a circuit connecting the output of filter 291, 765 cycles, through resistance 231, conductor I38, contact I43, conductor I39, resistance 293 and filter 293, 765 cycles, through the primary of transformer 224. follower, contact I44 is closed. This establishes a circuit connecting the output of filter 296, 595 cycles, through resistance 236, conductor I39, contact I 44, conductor I39, resistance 234, and band-pass filter 294, 595 cycles, through the primary of transformer 224.

The code combinations established by cams I3I to I34 and contacts I4I to I 44 to define the hundredths-degree settings of telescope I 9i are shown in Fig. 12. Combinations of alternating voltages of frequencies in accordance with the code shown in Fig. 12 are impressed through the secondary oi' transformer 224. They are amplified in amplifier 222 and impressed through transformers ZIB When cam I34 raises its.

12 and 2i 5 on the side circuit comprising conductors 369 and 36I. They are impressed through windings 392 and 394 of transformer 398 on amplifier 391. From the output of amplifier 391 they are impressed through transformer 3| I on the inputs of band-pass filters 3I3 to 3! inclusive, each one of which is arranged to .pass a different one of the four frequencies.

Current of 595 cycles will be transmitted through band-pass filter 3I3. It will be amplified and rectified in amplifier-rectifier 322 and energize relay 33I. Currents of 765, 935 and 1105 cycles will pass through band-pass filters 3I4, 3I5 and 3I6 respectively. They will be amplified and rectified in amplifier-rectifiers 323, 324 and 325 respectively, and will energize relays 332, 333 and 334 respectively. When contacts I to I44 in Fig. 1 are closed, relays 33I to 334 respectively will be conditioned so that their respective armatures will be in engagement, with contacts 349, 342, 344 and 346. Under this condition ground 359 will be connected to the armatures of these relays. When contacts I to I44 areopen relays 33I to 334 will be conditioned so that their respective armatures will be in engagement with contacts L343, 345 and 341 respectively. Under this condition battery 358 will be connected to the armatures of'the relays. Relays 33I to 334 will be conditioned in accordance with the code combinations shown in Fig. 12 when the line of sight through telescope IN is in the hundredths position indicated in Fig. 12.

When the armature of relay 33I is operated to close contact 349, a circuit is established from ground through contact 349, conductor 459, and the windings of relays 49IA, 49IB, 49IC, 49ID, 49 IE and 49 IF to battery actuating the armatures of these relays toward the left. When the armature of relay 332 is operated to engage contact 342, a circuit is established from ground 359 through contact 342, conductor 452,1Wlndlngs of relays 492A, 4923 and'the top windings of relay 492C to battery, actuating the armatures of relays 492A and 492B to the left: When the armature of relay 333 is actuated to close contact 344, a circuit is established from ground 359 through contact 344, conductor 454, winding of relay 493A and the top winding of relay 493B to battery actuating the armature of relay 493A to the left. When the armature of relay 334 is actuated to close contact 346, a circuit is established from ground through contact 346, conductor 456, winding of relay 494A, top winding ofrelay 4943 and the bottom windings of relays 595, 594, 593, 592 and 59I to' 65-volt battery 526. The armature of relays 494A will be actuated to the left. The manner in which relays 492C, 4933, 4943 and SM to 595, all of which have more than one winding, are affected by the operation of relays 33I to 334 will be described hereinafter.

When the armatures of relays 3'3I to 334 are actuated so as to close their respective contacts MI, 343, 345 and 341, -volt battery 358 will prises five groups of ten. One group of fifty ineludes all groups of ten the first digit of the first number of which is odd. The other includes all groups of ten the first digit of the first number of which is even so that consecutive tens in each group of twenty are in difierent groups of fifty.

The five tens in the left-hand vertical column I code combinations for the first ten consecutive numbers in a group of twenty are repeated in reverse order for the second ten consecutive numbers in a group of twenty. This is apparent from a'comparison of the ten top and ten bottom horizontal divisions of Fig. 12. The code combination for for instance in the upper group which corresponds to 95, 15, 35, 55 and '75 is the same as the code combination for 4 in the lower group which corresponds to 14, 34, 54 and 74. The code combination for 6 in the upper group is the same as that for 3 in the lower group, etc.

There are ten distinctive codes shown in the table per Fig. 12. There are ten corresponding distinctive selecting paths through the hundredths selecting circuit which, as has been mentioned, is the upper selecting circuit in Fig. .4. Since each code combination corresponds to one particular number'in each of five groups of ten consecutive numbers and to another particular number in each of five other groups of ten consecutive numbers, each of the corresponding ten selecting paths will efiect ten parallel selections consisting of two lamps in each of five groups of twenty, each of which 2 is in a different group of ten in the hundredths lamp bank 600 in Fig. 6. The selection of the particular lamp corresponding to the hundredth of a degree setting of the measuring instrument will be completed by the cooperation of the tenths selecting circuit which will simultaneously select a particular one of ten groups of ten consecutive lamps in the bank.

The various selecting paths through the selecting circuit per Fig. 4 for the hundredths of a degree will now be traced. Since the selecting paths do not extend through the armatures of relays 402C. 4033 and 4043 the description of the efiect of the operation of these relaysin response to the code signals will be deferred.

Refer to the top horizontal division of Fig. 12. This shows the code combinationfor the hundredth degree ending in the digit 5 in each of five of the ten one-tenth degree zones in each degree. The corresponding tenths zones are indicated in the upper half of the vertical column at the left of Fig. 12. The same code combination is shown in the bottom horizontal division of Fig. 12 which is the code for the digit 4 in each of five other of the ten one-tenth degreezones in each de- -gree. The corresponding tenths zones are indicatedin the lower half of the vertical column at the left of Fig. 12. Since none of the rectangles in the top horizontal line of Fig. 12 is cross-hatched, the armature of each of the re-- lays in the hundredths selecting circuit is actuated to close its right-hand contact. Under this condition a circuitmay be traced from battery 800 through resistance "I, contact 432, contact 428, contact 8, contact 408 and conductor 4" which connects to the top terminal of lamp and lamp i4 in the first group of twenty lamps in lamp bank 604 and which is multiplied to two lamps in corresponding positions in each of four other groups of twenty lamps, not shown in detail in lamp bank 800. but the numbers of which are indicated in the left-hand vertical column of the code diagram per Fig. 12.

The second horizontal division from the top in Fig. 12 shows the code combination for the digit 6 in live of the ten groups of ten, which code combination appears also in the second division from the bottom where it identifies the digit 3 in five other groups of ten. According to the code, the armatures of relays 402A and 4023 in the hundredtlis selecting circuit will be actuated to the left. The armatures of the other relays in the hundredths selecting paths will be actuated to the right. Under this condition a circuit may be traced from battery 800 through resistance 80L contact 432, contact 428, contact 4", contact 408 and conductor 482 to the top. terminal of lamp 88 and lamp i3 in the first group of twenty lamps in the lamp bank 600. Conductor 482 is multiplied also to the top terminals of each of two lamps in positions corresponding to the positions of lamps 86 and I 3 in each of four other groups of twenty lamps as indicated in the code diagram per Fig. 12.

Reference to the third horizontal division from the top in Fig. 12 shows the code combination for 7 in five groups of ten and reference to the third division from the bottom shows thesame code combination for 2 in five other groups of ten. Under this condition the armatures of relays 402A, 4023 and 403A in the hundredths selecting circuit per Fig. 4 will be actuated to the left. The armatures of other relays in the selecting paths for the hundredths lamps will be actuated to the right. A circuit may therefore be traced from battery 80!! through resistance 8M, contact 432, contact 421, contact-4H1 and conductor 48! which connects to the top terminals of lamps 91 and I2 in lamp group 95 to M. Conductor "I will connect to the top teminals of two lamps in positions corresponding to the positions of lamps 91 and 12 in lamp group 95 to M in each of the other four lamp groups in lamp bank 600 as indicated in the left-hand vertical column of Fig. 12.

The code combination for the digit 8 in five groups of ten is shown in the fourth division from the topin Fig. 12. The same code combination identifies the digit 1 in five other groups of ten. For this combination the armatures of relays 402A, 4023, 403A and 404A will be actuated to the left. The armatures of the other relays in the selecting paths for the hundredths lamps will be actuated to the right. Under this condition, a circuit may be traced from battery 800 through resistance 80l, contact I, contact 9, contact 4 and conductor 419 which connects to the top terminal of lamp 98 as well as to the top terminal of lam il inlamp group 95 to H. -Conductor 419 will be connected also to the top terminals of two lamps in corresponding positions in each of the other lamp groups as indicated in the left-hand vertical column of Fig. 12.

Reference to the fifth horizontal division from v the top in Fig. 12 shows the code for the digit 9 in five groups often. Reference to the fifth horizontal division from the bottom of Fig. 12 indicates that the same code identifies in five other groups of ten. For this code combination, thearmatures of relays 403A, 403B, 404A and 4043 will be actuated to the left. The armatures of other relays in the selecting paths for the hundredths lamps will be actuated to the right. Under this condition a circuit may be traced from battery 800 through resistance 80I, contact "I, contact 420, contact M2 and conductor 400 which connects to the top terminal of lamps 00 and I0 in lamp group 95 to I4 and is multiplied to the top terminals of two lamps in corresponding positions in each of the other four lamp groups.

Reference to the sixth horizontal division from the top in Fig. 12 shows the codefor the 0 digit in five groups of ten. Reference to the sixth horizontal division from the bottom in Fig. 12 indicates that the same code identifies digit 9 in five other groups of ten. For this combination the armatures of relays 40IA to 40IF, 402A and 404A will be actuated to the left. The armatures of the other relays in the selecting paths for the hundredths lamps will be actuated to the right. For this code combination a circuit may be traced from battery 800 through resistance 80I, contact "I, contact 420, contact 4 and conductor 485 which connects to the top terminal of lamp I00 and of lamp 09 in lamp group 95 to I4. Conductor 485 is multipled to thetop terminals of two lamps in positions corresponding to the positions of lamps I00 and 09 in each of the other four lamp groups as indicated in the left-hand vertical column of Fig. 12.

Reference to the seventh horizontal division from the top in Fig. 12 shows the code combination for digit 1 in five groups of ten and reference to the seventh horizontal division from the bottom indicates that the same code combination identifies digit 8 in five other groups of ten. For this code combination, the armatures of all of the relays in the hundredths selecting circuit will be actuated to the left. A circuit may therefore be traced from battery 800 through resistance 00I, contact 43I, cont-act 4| 9, contact M3 and conductor 484 which connects to the top terminals of lamps 0| and 08 in lamp group 95 to I4 and to corresponding terminals in each of the other four lamp groups as indicated in the left-hand vertical column of Fig. 12.

Reference to the eighth horizontal division from the top in Fig, 12 shows the code combination for digit 2 in five groups of ten and reference to the eighth horizontal division from the bottom indicates that the same code combination defines digit '7 in five other groups of ten. For this combination the-armatures of relays 40IA to 40 IF, 402A, 402B and 403A will be actuated to the left and the armatures of other relays in the selecting paths for the hundredths lamp will be actuated to the right. Under this condition, a circuit may be traced from battery 800 through resistance 80I, contact 432, contact 421 and contact 409 to conductor 486 which connects to the top terminal of lamps 02 and 01 in lamp group 95 to I4 and to two lamps in corresponding positions in each of the other four lamp groups.

The ninth horizontal division from the top in Fig. 12 shows the code combination for digit 3 in five groups of ten and the ninth division from the bottom shows that the same combination identifies digit 6 in five other groups of ten. For this combination the armatures of relays 40IA to -40IF and 402A to 402C will be actuated to the left. The armatures of other relays in the selecting paths for the hundredths lamps will be actuated to the right. Under this condition, a circuit may be traced from battery 800 through resistance 8!, contact 432, contact 428, contact 4i! and contact 401 to conductor 481 which connects to the top terminal of lamps 03 and 06 in lamp group to I4 and to the top terminals of two lamps in corresponding positions in each of the other four lamp groups as indicated in the left-hand vertical column of Fig. 12.

Reference to the tenth division from the top shows the code for digit 4 in five groups of ten and reference to the tenth division from the bottom shows that the same combination identifies digit 5 in five other groups of ten. For this combination the armatures or relays 40IA to 40IF will be actuated to the left. The armatures of other relays will be actuated to the right. A circuit may then be traced from battery 800, through resistance 00I, contact 432, contact 428, contact 4I8, contact 405 and conductor 488 which connects to the top terminals of lamps 4 and 5 in lamp group 95 to I4 and to the top terminals of two lamps in corresponding positions in each of the other four lamp groups. Reference to the left-hand vertical column of Fig. 12 indicates the numbers of the lamps in the various groups.

It has been shown that the top terminal of each of ten lamps is selected by each selecting path in the hundredths selecting circuit, One lamp is in each group of ten consecutive lamps. In order to complete the selection of any particular lamp it is necessary to select the particular group of ten corresponding to the measurement. This is the function of the tenths selectin circuit shown at the bottom of Fig. 4 which will now be explained.

Transmission of five element code signals Alternatin currents of the five frequencies passed by filters 205 to 209 in Fig. 2 are'employed in one five-element permutation code, shown in 208, are connected at all times to the contactsv controlled by the tenths of a degree cams I2I to I24. The fifth conductor I26 which connects to the output of filter 209 is not connected to the tenths of a degree cams. Reference to Fig. 13 which shows the ten five-element code combinations employed to define the ten tenths of a degree shows, in the right-hand vertical column, that the ten code combinations chosen for the ten tenths of a degree all use a no-current condition as the fifth element of the code. The reason for this will become apparent below. As the azimuth instrument changes through each degree, each of the ten code combinations. shown in Fig. 13 will be established in sequence as shown in the figure, The four cams I2I to I24 Will control their respective contacts in accordance with the four left-hand vertical columns in Fig. 13. The output from filter 209 which supplies current having a frequency of 1105 cycles will remain disconnected from the lower side circuit so that the fifth element of the five-element code will remain a no-current element for all ten of the tenth of a degree combinations.

- Currents having various combinations of fre- 17 quencies in accordance with the tenth of a degree codes, but never including frequency oi 1105 cycles, will be impressed through filters 2I0 to M3, transformer 226, lower side-band amplifier 22I, transformers 2I'8 and 2H, conductors 362 and 363, windings 303 and 308 of transformer 389, amplifier 3|0, transformer 3I2, band-pass filters 3 to 320 and amplifier rectifiers 326 to 329 to control the armatures of relays 335 to 338.

Since current of 1105 cycles is never transmitted to define tenths of a degree, relay 339 will remain deenergized whenever tenths of a degree code combinations are being transmitted.

Before proceeding with the tracing of selecting paths for the tenths of a degree selections the manner in which the five-element code combinations which define the twenty full degrees are transmitted will be described.-

All five of the conductors I26 to I30 which connect to the outputs'of filters 205 to 209 instead of being connected directly to the five full degree cam contacts II6 to I are connected to contacts I68, I66, I64, I62 and I60 of a multiple switch. The contacts are normally open. They are closed to connect the output of filters 205 to 209 to the full degree contacts only through a range of six hundredths of a degree, when the observing instrument is in the position from 97 hundredths to 02 hundredths of a degree. Shortly before the observing instrument moves into the hundredths zone from 9'1 to 02 in any degree, both on increasing and decreasing measurement-s, cam I will move switch arm I'45 clockwise about fixed pin I10; Switch bar I12 will rotate angle levers I14 to I18 clockwise about 1 rod I19 against the influence of individual springs such as I80 to close contacts I60, I62, I64, I68 and I68 during this interval. At such times the various five-element current and no-current code combinations which have been set up in advance on contacts II6 to I20 by cams III to I15 to define the particular one of the twenty full degree settings of the azimuth instrument in each of the eighteen different ZO-degree zones will be transmitted over the path traced for the lower side circuit. Since the various code combinations employed to define the full degrees includes signal elements in which the fifth element is a current condition which is evident from the righthand column of Fig. 14, current of 1105 cycles will be included in various combinations. It will be passed through side-band filters 2I4 in Fig. 2.

and 32I in Fig. 3, amplified and rectified in amplifier-rectifier 330' to energize relay 339.

A current condition, indicated by a crosshatched rectangle in Fig. 13, for an element in a code combination for the tenths of a degree, or n Fig. 14 for a full degree code combination,

will energize the corresponding relay of the group 335 to 339 and will operate the corresponding armature to engage its upper contact. For a no-current condition indicated by a blank rectangle in Figs. 13 or 14 the corresponding armature will be operated to engage its lower contact.

At this point attention is called to the fact that relays 335 to 339 receive the code combinations for both tenths of a degree and full degrees. The relays impress the code combinations on paths which extend through the windings of selecting relays in the tenths of a degree selecting circuit in the lower portion of Fig. 4 and in series through the windings of selecting relays in the full degree selecting circuit in Fig. 5. The full degree selecting circuit is ordinarily locked so that it cannot respond to the tenth degree com- 18 binations- The tenth of a degree selector per. Fig. 4 is disabled so that it is -unaifectedtby the full degree combinations when full degree combinations are registered in the full degree selector per Fig. 5. During the interval while the tenths of a degree selector is disabled a holding circuit maintains the proper tenth of a degree. that had been selected prior to the time the tenths of a degree selector was disabled so that, in effect, the proper tenth of a degree which is the tenth of a degree in the zero tenths zone or, more properly in this embodiment in the range from to 04 hundredths of a degree, is maintained at the recording station while the proper code combination for the particular full degree is being impressed on the full degree selector per Fig. 5. How this condition is eilected will be made apparent below. However, first the selecting paths which are controlled by relays 335 to 339 in both the tenths of a degree selector in the lower part of Fig.4 and the full degree selector in Fig. 5 will be traced.

When the armature of relay 335 engages contact 348 a circuit may be traced from ground through contact 348, conductor 458 into Fig. 4 through the windings of relays 42IA to 42IE, conductor 5I'0, into Fig. 5 and through the top winding of relay 520 to positive battery 525. When the armature of relay 336 engages contact 350 a circuit may be traced from ground 359 through contact 350, conductor 460 into Fig. 4, windings of relays422A to 422C, conductor 509 into Fig. 5 and through the top winding of relay 52I to positive battery 525. When the armature of relay 331engages contact 352 a circuit may be traced from ground 359 through contact 352, conductor 462 into Fig. 4, windings of relays 423A and 423B, conductor 508 into Fig. 5 and through the top winding of relay 522 to positive battery 525. When the armature oi. relay 338 engages contact 354 a circuit may be traced from ground 359 through contact 354, conductor 464 into Fig. 4, winding of relay 424A, conductor 501 into Fig. 5 and through the top winding of relay 523 to positive battery 525. When the armature of relay 339 engages contact 356 a circuit may be traced from ground 359through contact 356, conductor 466, winding of relay 425A, conductor 506 into Fig. 5 and the top winding of relay 524 to positive battery 525. When the armature of relays 335 to 339 are actuated to engage their lower contacts 349, 35I, 353, 355 and 359 respectively, positive battery 358 is connected to the originating end of each of these paths. The magnitude of the voltage of positive battery 358 is substantially greater than the magnitude of positive battery- When full degrees are defined, although the relays 42IA, 42IB, 42ID, 42IE, 422A, 4223, 422C, 423A, 4233, 424A, and 425A in the tenth of a degree selector respond, the response will not be effective to change the selection of the tenth of a degree in the range from 95 hundredths to 04 hundredths because relay 920 in Fig.4 acts as a holding relay for the zero tenth degree zone in a manner to be described later.

When tenths of a degree code combinations are transmitted the selecting relays in Fig. tend to respond but are locked in a manner to be described and cannot. When full degree codes are being transmitted the selecting relays in Fig. 5 are unlocked. At such times in response to the connection of ground 358 the armatures of selecting relays 520 to 524 are actuated to the left and when battery 356 is connected the armatures of relays 520 to 524 are actuated to the right.

Operation of the tenths of a degree selector The top horizontal line in Fig. 13 shows the code combination for the selecting of the tenths of a degree lamp group from 95 to 04 in lamp bank 600 in Fig. 6. For this combination each of the rectangles representing a signal element in the five-element code is blank and the armatures of all of the relays in the tenths selector will be actuated to engage their right-hand contacts.

The selecting path through the tenths selector extends through contact 429 of relay 802 and contact 426 of relay 402C. Regardless of the positions of these armatures the path which extends through contact 416, contact 414, contact 410 and contact 448 ends in an open circuit at contact 442. In the case of each of theother nine paths which extends through the tenths selector circuit, each of which will be traced hereunder, grounds B02 and 803 will be connected in parallel to the top terminal of some one of resistances 90! to 909 and to the inner terminal of a diii'erent one of nine diiferent groups of ten lamps each in lamp bank 600. The armature of relay 920 is biased by a circuit which extends from battery 925 through the bottom winding of relay 920 to ground to engage contact 416 when the top winding of relay 920 is not energized. When any one of the nine continuous paths through the tenths selecting circuit is established the ground connected thereby to the corresponding one of the top terminals of resistances 90! to 909 meets batter connected to the right-hand terminal of the top winding of relay 920 and the armature of relay 920 will be actuated to the left. When the selecting path through the tenth selecting circuit for the tenth degree in the range from 95 to 04 is open and the armature of relay 920 engages contact 416 a circuit'may be traced from ground 804 through the armature of relay 920, contact 416, conductor 499 into Fig. 6 to the inner terminal of the ten lamps in lamp group 95 to 04. Thus it should be apparent that the code combination of five no-current signal elements which is the combination for lamp group 95 to 04 results in an open selecting path through the tenth of a degree selecting relays and that for this condition the armature of relay 920, which is in engagement with contact 415 for all other of the nine possible tenth degree selections, will engage contact 416 to eirect the selection of lamp group 95 to 04 which is called the zero tenths selection.

When any one of the nine other selecting paths through the tenths selector is closed, in a manner to be described, the armatuer of relay 920 will be operated to engage with contact 415. A circuit may then be traced from ground 804 through contact 415, bottom winding of relay 404B, bottom winding of relay 403B, bottom winding of relay 402C, conductor 5 into Fig. 5 and the top windings of relays 505, 594, 503, 502 and 50!. When current flows in this path it is dominant over current flowing through the other winding of each of these relays when the paths through such windings are closed. In response to current of such polarity flowing through its bottom winding the armature of relay 4043 will be actuated to the right. The armature of relay 4033 will be actuated to the left. The armature of relay 4020 will be actuated to the right. The armatures of relays 50! to 505 will be actuated to the left to lock the full degree selector in algnanner to be described. The efiect of the operation of the armature of relay 404B will be described below. The operation of the armature of relay 4033 connects ground to one of the two branches at the apex of the tenths of a degree selecting circuit. The operation of the armature of relay 402C to the right connects ground to the other of the two branches at the apex of the tenths of a degree selecting circuit. Ground will thus remain connected through these two parallel branches which form the apex of the tenths selecting circuit during the entire interval while the observing instrument is in the range from 05 to 94 hundredths in each degree. At other times the armatures of relays 4033 and 4020 are under the influence of their respective top windings. These in turn are under the influence of the hundredths of a degree cams for a reason to be explained.

The second horizontal line in Fig. 13 shows the code combination for tenth of a degree lamps 05 to H. For this condition, the armatures of relays 42 IA to 42 IE are actuated to the left. The arma tures of other relays in the selecting paths in the tenths selecting circuit are actuated to the right. A circuit may then be traced from grounds 802 and 903 in parallel throughcontacts 429 and 426 in parallel, contact 418, contact 414, contact 410, contact 448, contact 4 and conductor 496 to parallel branches. One branch extends through resistanc 903 and the top winding of relay 920. This operates the armature of relay 920 to engage contact 415 asexplained above. The opening of contact 416 disconnects ground from conductor 499 which is connected to lamps 95-04. The second branch connects through conductor 495 to lamps 05i4.

It is emphasized that whenever grounds 602 and 803 are connected through a particular selecting path in the tenths selecting circuit to any one of the nine selecting conductors 490 to 498 to chest a selection of a particular group of ten lamps in lamp bank 600, a parallel path is established through someone of resistances l to 909 which connects to the top winding of relay 920. In each such instance, therefore, the armature of relay 920 will be disengaged from contact 416. Grounds 802 and 803 in parallel will be supplied for nine of the ten tenths selections of lamp bank 600 and ground 804 will be supplied for the tenth selection, namely, the selection of the tenths group -04.

The third horizontal division from the top in Fig. 13 indicates that the armatures of relays 42 IA to 42 IE and 422A to 422C are all actuated to the left and the armatures of the other relays in the selecting paths in the tenths selecting circuit are actuated to the right. A circuit may then be traced from grounds 802 and 003 in parallel through contacts 429 and 426 in parallel, contact 418, contact 414, contact 410, contact 441, contact 499 and conductor 494 which connects to the inner terminal of lamps l524.

The fourth horizontal division from the top in Fig. 13 indicates that the armatures of relays 422A to 422C are actuated to the left. The armatures of the other relays in the selecting paths in the tenths selecting circuit will be actuated to the 421A to 42lE, 422A to 422C,

21 right. A circuit may, therefore, be traced from grounds 802 and 808m parallel through contacts 429 and 428 in parallel, contact 418, contact 414. contact 410, contact 441, contact 440 and conductor 488 which connects to the inner terminals of lamps 28-84.

The fifth horizontal division from the top in Fig. 13 indicates that the armatures of relays 4224. to 422C and 428A and 4233 will be actuated to the left. The arma'tures of the other relays in the selecting paths in the tenths circuit will be actuated to the right. A circuit may then be traced from grounds 802 contacts 429 and 428 in parallel, contact 418, contact 414, contact 489, contact 445, contact 438 and conductor 49! which connects to the inner terminals of lamps -44.

The sixth horizontal division from the top in and 803 in parallel through Fig. 13 indicates that the armatures of relays 423A and'423B are actuated to the left. The armatures of the other relays in the selecting paths for the tenths selector will be actuated to the right. then be traced from grounds 802 allel through contacts 429 and 428 in parallel, contact 418, contact 414, contact 469, contact 445, contact 435 and conductor 490 which connects to the inner terminals of lamps -54.

The seventh horizontal division from A circuit may the top in Fig. 13 indicates that the armatures of relays 421.4 to 425E. 423A and 4233 will be actuated to the left. The armatures of the other relays in the selecting paths of the tenths selector will be actuated to the right. Ascircult may, therefore. be traced from grounds through contacts 429 and 428 in parallel. contact 418, contact 414: contact 469, contact 446, contact 431 and conductor 492 which connects to the inner terminals of lamps -84.

The eighth horizontal division from the top in I Fig. .13 indicates that the armatures of relays 423A and 4233 will be actuated to the left. The armatures of the other relays in the selecting paths of the tenths selector will be actuated to the rght. A circuit-may then be traced from grounds 802 and 803 through contacts 429 and 428 in parallel. contact 418, contact 414, contact 489. contact 448, contact 438 and conductor 493 which connects to the inner terminals of lamps 85-14.

The ninth horizontal division from the top in Fig. 13 indicates that the armatures of relays and 803 in par- 802 and 803 in parallel 423A, 4233 and 424A will be ac'tua-tedto the left. I

The armatures of the other relays in the selecting paths of the tenths selector will be actuated to the right. A circuit may then be traced from grounds 802 and 809 through contacts 429 and 428 in parallel, contact 418, contact 413, contact 468, contact 444, contact 4' and conductor 491 which connects to the inner terminals of lamps 15-94.

The bottom horizontal division in Fig. 13 indicates that the armature of relay 424A will be actuated to the left. The armatures of the other relays in the selecting paths of the tenths selector will be actuated to the right. A circuit'may then be traced from grounds 802 and 808 in parallel through contacts 429 and 428 in parallel. contact 418, contact "3, contact 488, contact 444, contact 412 and conductor 498 which connects to the inner terminals of lamps -94.

It was shown that the one-hundredths selecting apparatus connected battery to the outer terminal of a particular lamp in each of the ten roups of lamps in lamp bank 800. A circuit to round will be available at any one time in onli lamp bank 800 is divided and the one-hundredths selector and the tenths selector, therefore, cooperate to light a particular one of the one hundred lamps in lamp bank 900.

Reference to Fig. 14 shows the code combinations for the full degrees from 0 to 19 in each 20- degree zone. Each code combination for each of the twenty degrees as has been shown is impressed on the same side circuit which is used for the tenth of a degree selections during a portim of the interval while the tenths of a degree selecting circuit is selecting the tenth of a degree in the range from -04 at which time all of the tenths of a degree cam contacts are open. At this time, as has been explained, there is no continuous path through the tenths of a degree selector. The armature of relay 920, is. therefore actuated to the right and the tenths of a degree lamps in the range 95-04 are selected for the l-cycle current as the fifth element of the five-element code shows that for sixteen of the twenty full degree selections, viz., from 4 to 19, inclusive, current of 1105 cycles is impressed on the line. For this condition the armature of relat 399 will be operated to close contact 356. Under this condition the armature of relay 425A will be actuated to the left to open contact 418. Ground will, therefore, be disconnected from each of the nine selecting paths which extend through contact 418. As a result of this, even though the various relays in the tenth of a degree selecting circuit respond to the full degree codes, there can he no continuous path for any of the nine selections which will pass through contact 418 and the lamp group from 95 to 04 will remain selected as contact 416 which connects ground 804 to conductor 499 remains closed.

Reference to the top four horizontal divisions in Fig. 15 corresponding to the codes for the full degrees from 0 to 3, in the first ZO-degree zone and to corresponding full degrees in each of the other zones, inclusive, shows that for this condi- (ion the armature of relay 428. will be actuated to the right to close contact 418. However, for this condition, whatever the positions of the armatures of relays 402C and 403B, each of the paths through the tenths of a degree selector corresponding to each of these full degree codes extends to an open circuit notwithstanding the closure of contact 418. This will now be demonstrated.

Reference to the top horizontal division of Fig. 14 shows that for. zero full degree the armatures of relays 422A to 422C and 424A will be actuated to the left. If ground is connected to the armature of relay 425A at such time, a circuit extends I through contact 418 and contact 413 to opena In accordance with the code for full degree 2.

the armatures of relays 42|A to 42IE, 422A to 

